The processes of drug induced carcinogenesis and mutagenesis and their relationship to DNA binding will be studied by the technique of photoaffinity labeling of intact cells. The azido analogs of the fluorene class of carcinogens will be synthesized, and after study of their photodecomposition in vitro will be photolyzed to the active nitrene in intact bacterial cells and in the skin of mice. Due to the presumed binding of the hydrocarbon to DNA, its photolysis to the reactive nitrene in vivo should identify its precise locus of binding in relation to mutation induction and carcinogenesis. Both mutation induction using frameshift tester strains of Salmonella; and skin carcinogenesis in mice will be studied by direct application of the drugs with and without photolysis. Thus, the covalent binding theory for carcinogenesis will be studied directly both with respect to drug binding under precisely controlled conditions of drug activation, and in relation to mutation induction.